This disclosure relates to vapor deposition of materials, including chemical vapor deposition (CVD), atomic layer deposition (ALD), spray pyrolysis (SP) and misted deposition (MD).
In CVD processes, vapors of one or more precursors are directed over a substrate on which material is deposited as a product of chemical reaction(s) of the precursor vapor(s).
In ALD processes, two precursor vapors are alternately directed onto a surface on which their reaction product is deposited.
In SP processes, droplets of a liquid or solution of the chemical precursor are directed at a heated substrate on which a material is deposited.
In MD processes, droplets of a liquid or solution are directed onto the surface of a substrate on which they coalesce to form a liquid film. This wet substrate is then treated or cured by heating, irradiation with light or other means to induce reaction to produce the desired material on the substrate.
When a precursor is a solid material, a solvent is often used to dissolve the precursor. Then the solution of the precursor is used in one of these processes. The solvent must be chosen so that its presence does not interfere with the deposition process. It may be chemically inert in the conditions of the deposition, or it may even contribute to the chemical process as a reagent.
It has been found in practice that it is very difficult to find solvents that meet all the requirements for deposition processes using these solutions.